Prognostic Meteorological Discussion
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FXAK02 KWNH 301926
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
326 PM EDT MON MAY 30 2016

VALID 12Z FRI JUN 03 2016 - 12Z TUE JUN 07 2016

THE PATTERN FOR NEXT WEEKEND STARTS WITH A BLOCK IN PLACE WITH A
PERSISTENT UPPER HIGH OVER NORTHEASTERN RUSSIA AND A CLOSED LOW
OVER THE ARCTIC OCEAN.
A TRAILING TROUGH EXTENDS FROM THE ARCTIC COAST TO THE GULF OF
ALASKA.

THE MODELS ARE COMING INTO INCREASED AGREEMENT ON A 500 MB
SHORTWAVE MOVING SOUTH NEAR THE SOUTHWEST AK COAST AND ACROSS THE
ALEUTIANS NEXT WEEKEND AND INTO THE ADJACENT NORTH PACIFIC EARLY
NEXT WEEK. A CLOSED LOW IS FORECAST TO DEVELOP WITH
SPREAD DEVELOPING ON THE TIMING AND WHETHER ADDITIONAL LOWS
DEVELOP AROUND THE BROADER CIRCULATION EARLY NEXT WEEK.

THE 00Z ECMWF WAS FASTER IN MOVING THE HEIGHTS/PRESSURES EAST
ACROSS THE NORTH PACIFIC...WITH ITS ENSEMBLE MEAN SEVERAL HOURS
SLOWER NEXT MON 06 JUN-TUE 07 JUN.
THE 12Z ECMWF RUN TRENDED SLOWER TOWARDS THE MEAN SOLUTION.
THE 06Z GEFS MEAN AND 00Z CANADIAN ENSEMBLE MEAN ARE EVEN SLOWER
THAN THE ECMWF ENSEMBLE MEAN.  THESE SOLUTION LINE UP WELL WITH
TELECONNECTIONS FROM THE POSITIVE HEIGHT ANOMALY OVER NORTHEAST
RUSSIA...WHICH SUGGEST PERSISTENT NEGATIVE HEIGHT ANOMALIES
PERSIST OVER THE ALEUTIANS/ADJACENT NORTH PACIFIC.

THE 06Z RUN OF THE GFS WAS AN OUTLIER IN DEVELOPING A SECONDARY
AREA OF CLOSED HEIGHTS/PRESSURES OVER THE ARCTIC OCEAN...WITH
HEIGHTS MUCH LOWER THAN THE ECMWF/CANADIAN GLOBAL/GEFS ENSEMBLE
MEANS.  CONFIDENCE IS LOW IN THE GFS FCST OF A CIRCULATION OVER
THE WEST COAST OF AK 12Z SUN 05 JUN THAT THEN CONTINUES SOUTHWEST
INTO THE BERING SEA MON 06 JUN AND TUE 07 JUN.  WITH THE GEFS MEAN
LINING UP WELL WITH THE OTHER MEANS...THE 06Z GFS LOOKS LIKE A LOW
PROBABILITY SOLUTION AND WAS GIVEN THE LEAST WEIGHTING.
LIKEWISE..THE ECMWF MADE AN ABRUPT CHANGE ON THE 12Z CYCLE WITH
MUCH LOWER HEIGHTS/PRESSURES IN THE ARCTIC OCEAN EARLY NEXT
WEEK...SO CONFIDENCE IS LOW IN THE CHANGE GIVEN THE LACK OF
SUPPORT FROM THE OTHER MODELS AND ITS OWN ENSEMBLE MEAN.

MANUAL PROGS ACROSS THE DOMAIN BLENDED THE ENSEMBLE MEANS BECAUSE
OF THE UNCERTAINTIES WITH INDIVIDUAL OPERATIONAL MODEL RUNS AS
DESCRIBED ABOVE.


PETERSEN

$$





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